The following is a tabulation of some prior art that presently appears relevant:
PatentKindIssueNumberCodeDatePatentee8,621,010B22013William Brittles, Paul AndrewDec. 31TITHERIDGE, Nathalie DE MEYER,Christopher MATTHEWSON, SimonGORMLEY7,617,284B22009Goran SalamuniccarNov. 107,380,126B22008James D. Logan, Charles G. CallMay 277,359,941B22008Christopher Hoang Doan, LilianaApr. 15Orozco
Email is one of the most used forms of communication. However, majority emails received in the inbox are regular spam emails, known as unsolicited bulk emails. According to Cyren (www.cyren.com) 2015 CYBERTHREAT YEARBOOK, The amount of average spam per day is 54.6 billion in 2014. The highest amount of single day is 107.9 billion regular spam emails sent on the 2nd of August that year. For email users, not only reviewing and deleting these unwanted messages take long time, but also may receive viruses from unknown senders. Spam costs multibillion dollars each year in lost productivity.
For years, there are many technologies proposed to fight spam, such as filtering out unwanted email messages by using a filter constructed from a collective input of the reviewing group of users, using Secure Anti-Spam Email Protocol (SASEP), counting total number of email messages sent by sender in a predetermined time period, determining if a message has a valid message structure for the destination, and other approaches based on regular email services. The major problem with these approaches is that spammers can send unwanted regular email to other email recipients, yet the recipient has no effective way of controlling unknown senders and unwanted regular emails. More and more regular spam emails reflect that these technologies are not fully successful yet.